1. Field
The present invention relates to a nonvolatile memory and a method of manufacturing a nonvolatile memory, and more particularly, to a structure of a single polysilicon electrically erasable programmable read only memory (EEPROM) capable of performing recording, deleting and reading operations at a low voltage, a method of manufacturing the same, and an operation method of the same.
2. Description of Related Art
As a nonvolatile memory device using a silicon semiconductor process, a dual polysilicon electrically erasable programmable read only memory (EEPROM), in which double layers of polysilicon are staked as a floating gate and a control gate, and a flash memory are generally used. Despite its small cell size, this stacked gate-type memory involves a complicated circuit and manufacturing process and thus is not proper for a low-density and low-cost memory.
Storage devices with a comparatively small memory capacity and inexpensiveness are needed in various fields using a radio-frequency identification (RFID) chip. Here, a single polysilicon EEPROM compatible with a complementary metal-oxide-semiconductor (CMOS) is generally used.
The single polysilicon EEPROM may be programmed by two methods. A first method is channel hot electron injection. According to a programming method using channel hot electron injection, a strong electric field is formed in a channel region between a source electrode and a drain electrode, and part of electrons having a high kinetic energy by the strong electric field pass through a potential barrier of an oxide layer to be injected into a floating gate. The electrons injected into the floating gate are isolated by a potential barrier of an insulating layer, resulting in an increase in a threshold voltage of the MOS.
A second method is Fowler-Nordheim (F-N) tunneling. According to a programming method using F-N tunneling, as a high electric field is applied to an oxide between a gate and a source/drain/well electrode, an tunneling current exponentially increases with respect to the electronic field. The high electric field may cause an F-N tunneling phenomenon of electrons in the MOS, so that electrons may be injected into the floating gate and the threshold voltage of the MOS may increase accordingly.